"""
AI 服务工厂
根据租户配置创建和管理 AI 客户端
"""
from typing import Optional
from cachetools import TTLCache
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.models.ai_config import AIConfig
from app.services.ai_client import OpenAICompatibleClient
from app.utils.crypto import decrypt_api_key


class AIServiceFactory:
    """
    AI 服务工厂

    根据租户的 AI 配置创建对应的 AI 客户端
    使用 TTL 缓存避免频繁创建客户端
    """

    # 客户端缓存，TTL 10 分钟
    _cache: TTLCache = TTLCache(maxsize=100, ttl=600)

    @classmethod
    async def get_client(
        cls,
        tenant_id: str,
        db: AsyncSession,
    ) -> Optional[OpenAICompatibleClient]:
        """
        获取租户的 AI 客户端

        Args:
            tenant_id: 租户 ID
            db: 数据库会话

        Returns:
            AI 客户端实例，未配置返回 None
        """
        # 检查缓存
        cache_key = f"ai_client:{tenant_id}"
        if cache_key in cls._cache:
            return cls._cache[cache_key]

        # 从数据库获取配置
        result = await db.execute(
            select(AIConfig).where(
                AIConfig.tenant_id == tenant_id,
                AIConfig.is_configured == True,
            )
        )
        config = result.scalar_one_or_none()

        if not config:
            return None

        # 解密 API Key
        api_key = decrypt_api_key(config.api_key_encrypted)

        # 创建客户端
        client = OpenAICompatibleClient(
            base_url=config.base_url,
            api_key=api_key,
            provider=config.provider,
        )

        # 缓存客户端
        cls._cache[cache_key] = client

        return client

    @classmethod
    def invalidate_cache(cls, tenant_id: str) -> None:
        """
        使缓存失效

        当租户更新 AI 配置时调用
        """
        cache_key = f"ai_client:{tenant_id}"
        if cache_key in cls._cache:
            del cls._cache[cache_key]

    @classmethod
    def clear_cache(cls) -> None:
        """清空所有缓存"""
        cls._cache.clear()

    @classmethod
    async def get_config(
        cls,
        tenant_id: str,
        db: AsyncSession,
    ) -> Optional[AIConfig]:
        """
        获取租户的 AI 配置

        Args:
            tenant_id: 租户 ID
            db: 数据库会话

        Returns:
            AI 配置模型，未配置返回 None
        """
        result = await db.execute(
            select(AIConfig).where(AIConfig.tenant_id == tenant_id)
        )
        return result.scalar_one_or_none()

    @classmethod
    async def create_or_update_config(
        cls,
        tenant_id: str,
        provider: str,
        base_url: str,
        api_key_encrypted: str,
        models: dict,
        temperature: float,
        max_tokens: int,
        db: AsyncSession,
    ) -> AIConfig:
        """
        创建或更新 AI 配置

        Args:
            tenant_id: 租户 ID
            provider: 提供商
            base_url: API 地址
            api_key_encrypted: 加密的 API Key
            models: 模型配置
            temperature: 温度参数
            max_tokens: 最大 token 数
            db: 数据库会话

        Returns:
            更新后的配置
        """
        # 查找现有配置
        result = await db.execute(
            select(AIConfig).where(AIConfig.tenant_id == tenant_id)
        )
        config = result.scalar_one_or_none()

        if config:
            # 更新现有配置
            config.provider = provider
            config.base_url = base_url
            config.api_key_encrypted = api_key_encrypted
            config.models = models
            config.temperature = temperature
            config.max_tokens = max_tokens
            config.is_configured = True
        else:
            # 创建新配置
            config = AIConfig(
                tenant_id=tenant_id,
                provider=provider,
                base_url=base_url,
                api_key_encrypted=api_key_encrypted,
                models=models,
                temperature=temperature,
                max_tokens=max_tokens,
                is_configured=True,
            )
            db.add(config)

        await db.flush()

        # 使缓存失效
        cls.invalidate_cache(tenant_id)

        return config


# 便捷函数
async def get_ai_client_for_tenant(
    tenant_id: str,
    db: AsyncSession,
) -> Optional[OpenAICompatibleClient]:
    """获取租户的 AI 客户端"""
    return await AIServiceFactory.get_client(tenant_id, db)